The valve disclosed, while useful in other applications is particularly well adapted for controlling the filling of above ground fuel storage tanks. These tanks are filled from tank trucks by means of a large diameter hose which is sealingly coupled to the upper end of the fill pipe during the filling operation. Because of the relatively large capacity of the storage tanks, a relatively high flow rate during the filling operation is desirable and flow rates in the general range of 400 gpm are typical. At these high flow rates, it is quite common the tank is overfilled resulting in a spill. As much as 35 gallons of fuel may be involved in such a spillage. To prevent this spillage from contaminating the soil, it is now required in many locations that the fill pipe be equipped with an overfill storage container. However, prevention of overfilling of the tank is obviously the most desirable solution.
Monitoring of the fuel level within the tank during the fill operation presents a problem in that the sole access to the interior of the tank is via the fill pipe. Various sensing devices which will give a continuous reading of the fuel level within the tank during the filling operation have been proposed, however, typically these devices give a gauge reading to the fuel delivery man, who may not be paying close enough attention to the gauge to prevent a spill.
To prevent overfilling, many present day above ground storage tanks are provided with a float actuated valve which closes when the level of fuel within the above ground storage tank rises to a predetermined level, for example when the tank is 95% full. Most of these valves stop the incoming flow of fuel, but a substantial quantity, typically 25 to 30 gallons of fuel, remains in the supply hose between the float actuated shut off valve at the fill pipe and the shut off valve on the tank truck.
Previously known float actuated shut off valves prevent the filling of the storage tank beyond its capacity, but they do not solve the main problem created by overfilling, namely, the trapping of 25 to 30 gallons of fuel in the supply hose between the fill pipe and the shut off valve on the tank truck. The present invention is directed to a solution to the aforementioned concern.